This invention relates to telephone switching systems in general and to circuits for generating calling station identification information. In particular, the invention relates to station identification equipment arranged to generate alternate station identification codes for billing purposes in accordance with the class of toll call being processed.
Arrangements in telephone communication systems for automatically identifying calling stations are well known. One such arrangement is described in U.S. Pat. No. 3,071,650, which issued to Cahill et al. on Jan. 1, 1963. In Cahill et al., in order to provide billing for toll calls, all traffic originating in small local exchanges and destined for the toll network is routed to a centralized tandem exchange, called a CAMA exchange, which is equipped with automatic message accounting, or AMA, facilities. In order to identify calling stations for the billing records accumulated at the CAMA exchange, each originating exchange is provided with automatic station identification (ANI) equipment, which identifies a calling station on request and transmits the identification information to the AMA facilities at the CAMA exchange. The ANI apparatus, although greatly effective for its intended purpose, is limited in that it is capable only of providing a single predetermined identification for each calling station. For example, in systems employing the Cahill et al teaching, a private branch exchange (PBX) customer may elect to have all toll calls automatically billed to the PBX general directory number, or the customer may elect to have manual operator identification of calling PBX stations so that the calls may be billed to the individual stations or to other desired special numbers. The customer may not, however, elect combinations of different billing schemes.
A need arises in certain situations to provide greater billing flexibility in order to best serve telephone customers. For example, many PBX customers desire that certain classes of toll calls originated from the PBX stations be billed to special identification codes, such as sales account numbers, and that other classes of toll calls be billed to the general PBX directory number. This arrangement whereby toll calls are billed to special codes dependent on the specific call in question is commonly referred to as Q-Z billing.
PBX customers may further desire that certain classes of toll calls be billed to individual PBX stations, whereas other calls be billed to the PBX general directory number.
Another example occurs with respect to small originating exchanges equipped for operation with an automatic message accounting and recording system (AMARS). The AMARS, which is described in 1976 Bell Laboratories Record 104, is designed to provide detailed billing records, similar to the records now provided by CAMA exchanges on toll calls, for local calls on the basis of actual usage of the network. For local traffic, the AMARS call monitoring equipment obtains call information, such as answer time and called party number, and communicates with automatic number identification equipment in the originating exchange to identify a calling station and to transmit this information to a centralized site for storage and processing. For CAMA exchange toll traffic, however, the AMARS is inoperative and billing information for this traffic is accumulated in a CAMA exchange which communicates with the local exchange ANI equipment to obtain calling station identification information as described in Cahill et al. A need has been expressed by certain customers served by an AMARS to have the billing of local calls directed to a general directory number, while allowing for Q-Z and individual station billing for CAMA traffic.